charging system HELP!

I just replaced both battery and alternator (Remy New from Advanced Auto) on my 2000 windstar. The car starts fine, but about 15 seconds after the engine started, the charging system indicator (the one with a battery sign) comes up. I need help on diagnosing this. One thing I should mention was that I forgot to disconnect the battery when I disconnected the alternator and there was a spark when the alternator wire touched the engine block. I don't know if this burned out any fuses or relays that are related to the charging system, and if so which one should I check?
Thanks!

AdvanceAuto can probably test the alternator in the vehicle for you ... I know my local AutoZone has this capability. I suspect you have burned out some diodes in the alternator.

I got the spark when the old alternator was in there. I may stop by the store to have them checked out anyway but I think it is likely that something else in the circuit is the culprit but do not know how to go about to diagnose.

Do you have access to a voltmeter? If so, test the "tops" of all fuses under the hood and in the cabin. Do this when engine is idling. When you find a voltage that is lower than battery voltage ... you may have found an open/blown fuse ... if not, report back with fuse number.

I just replaced both battery and alternator (Remy New from Advanced Auto) on my 2000 windstar. The car starts fine, but about 15 seconds after the engine started, the charging system indicator (the one with a battery sign) comes up. I need help on diagnosing this. One thing I should mention was that I forgot to disconnect the battery when I disconnected the alternator and there was a spark when the alternator wire touched the engine block. I don't know if this burned out any fuses or relays that are related to the charging system, and if so which one should I check?
Thanks!

What was your original symptoms that caused you to change your alternator and battery in the first place? I assume you just didn't' have $300 or so burning a hole in your wallet...

Also post back with your voltage readings directly from the battery terminals both with the car off and with the car running.

I'm guessing that the wire which shorted to the engine block was the main B+ terminal, because that's likely to be the only one which is uninsulated at the connector end. It's the real thick wire, and usually it fits over a large threaded stud on the alternator, secured by a nut. That wire runs between the alternator B+ (output) terminal and the battery positive terminal, carrying charging current to the battery. I think it's protected by a couple of fusible links, wired in parallel. Since a big lead-acid battery is capable of supplying many hundreds of amps under short-circuit conditions, there's a chance the fusible links might have blown when the cable shorted against the block.

I'd start by measuring the battery voltage with the engine off - it should be around 12.6V. Then start the engine, and check the battery voltage again. If it rises then the B+ cable and its fusible links must be ok, but if it falls then they could be open-circuit.

Easiest way to check the fusible links, assuming the alternator is reasonably accessible, is to check for 12V at the B+ connection at the alternator, using either a 12V test lamp or a multimeter on its DC voltage range. Don't have the engine running while doing that, and don't have the ignition switched on either, because 12V should always be present at the B+ terminal, even with engine and ignition switched off.

If you have 12V then the fault is elsewhere, but if you find 0V then the fusible links are open-circuit, and thus no charging current can reach the battery until they are replaced.

I'm assuming you didn't have this symptom prior to replacing battery and alternator - if it only started to happen after shorting the wire then I think that's the most likely cause.

The wire that was shorted was the one secured by a nut.

The original symptoms was kind of strange. The headlight and radio and everything electrical just kept turning off and turning back on and blinking and kept cycling on and off regardless of where the switches were. This happened when I was driving. Then it was back to normal for a day and then everything died a day after. After putting a new battery in, everything went back to normal, but I decided to replace the battery anyway since it was about 177K mi. old.

I just measured the battery voltage with a multimeter, and it was 12.6 when engine was off, and around 13.4V when engine was on. With the red wire of the meter at the alternator terminal with the nut and the black wire at the negative battery terminal, when engine OFF, it was around 12.6V.

So I take it that the wires and fuses are OK but the computer still detects a fault in the circuit. Is 13.4V too low of an output from the alternator?

The symptoms you mentions 'could' be a corroded or loose connection on either the B+ or the ground side of the circuits.
With a new battery, I am expecting that the common issue of corrosion on the battery terminals is not the case....but double check to make sure that the cable connections are tight.
Also....check the ground connections to the chasis and motor as well as the B+ connections at the starter and other locations.
Be careful with metal tools around the B+ connections......a momentary bump to the chasis will make some major sparks and you don't want to weld your wrench to the vehicle.

I just measured the battery voltage with a multimeter, and it was 12.6 when engine was off, and around 13.4V when engine was on. With the red wire of the meter at the alternator terminal with the nut and the black wire at the negative battery terminal, when engine OFF, it was around 12.6V.

So I take it that the wires and fuses are OK but the computer still detects a fault in the circuit. Is 13.4V too low of an output from the alternator?

The alternator voltage output has always frustrated me on my 2000 Windstar, I think Ford tried to overengineer this and made it way too complex. The alternator voltage output is directly controlled by the PCM (computer) and tries to keep the voltage as low as possible as to not "over charge" the battery and boil off the electrolyte. I believe the algorithm's in the PCM look at the battery "rest" voltage and then controls the field to the alternator on restart to arrive at a suitable output voltage to charge the battery but at a conservative low level.

If my Winnie sits for 3-4 days, the rest voltage will drop to 12.3 to 12.4 volts. When I start it, the alternator will read 14.4V (the max I've ever read) and stay there until I shut off the van. If I start it right back up, the voltage will be around 13.3V as the rest voltage only dropped to ~12.8 volts.

Bottom line is that the alternator output voltage will vary on each restart depending on how low the rest voltage got during the car off cycle. My output varies between 13.0V to 14.4V.

A reading of 12.6V at the alternator output terminal with the ignition switched off does indeed confirm that the B+ cable and fusible links are still intact.

I was going to say that 13.4V at idle seems a bit low, but considering the voltages which bdahl has observed on his year 2000 model, it's quite possible that that's entirely normal, so I wouldn't pursue that any further right now.

I agree with Wiswind that you could well have a bad connection somewhere. For the ground connections which Wiswind referred to, follow the cables from the battery negative terminal and you should find that a fairly heavy one bolts onto the engine block, while another bolts to the firewall or fender, and then there may or may not be other smaller ground wires - check in particular that the ground connections to engine and chassis are clean and secure.

You could also look at the engine compartment fuse panel and ensure that the panel itself is securely mounted, and that the fuses and relays are firmly seated in their sockets.

After the wire shorted against the block, I assume the first thing you did next was to disconnect the battery, in which case the PCM will have effectively had a reset. If however you proceeded with the battery still hooked up, then it might be worth giving the PCM a reset now by disconnecting the battery negative terminal for a few minutes, and then reconnecting it. The reason why I say that is because when the wire shorted, the battery voltage would have dropped significantly, if only briefly, below the threshold at which the various control modules, including the PCM, will operate reliably, so there might just be a glitch in the PCM which, as bdahl mentioned, is responsible for controlling the alternator's voltage regulator.

After the wire shorted against the block, I assume the first thing you did next was to disconnect the battery, in which case the PCM will have effectively had a reset. If however you proceeded with the battery still hooked up, then it might be worth giving the PCM a reset now by disconnecting the battery negative terminal for a few minutes, and then reconnecting it. The reason why I say that is because when the wire shorted, the battery voltage would have dropped significantly, if only briefly, below the threshold at which the various control modules, including the PCM, will operate reliably, so there might just be a glitch in the PCM which, as bdahl mentioned, is responsible for controlling the alternator's voltage regulator.

It's a good idea to do that. Try to reset the PCM to see if the battery light disappear. And also check for bad ground connections. A rusty bolt can cause you problems.

Your alternator seems working good and you don't need to check any fuse or relays.

I espect that your PCM is not broken.

I decided to exchange the alternator anyway for the same brand just rule out the possibility that it is bad, and surely it solved the problem of the battery light. By the way, I disconnected the battery wire after the spark so the PCM should be reset after when the first new alternator was installed.

The battery voltage at idle now with the second new alternator is around 14.4V, which is around 1V more than the other unit. I don't know if that matters.

Glad it worked out for you. I like 14+ volts a little better than 13+ volts for an auto generator ... but 15 volts, or higher, is too much.

I've been thru similar experiences with puchasing new or reman alternators that did not work. I've learned to have them bench tested, while I watch, before leaving the parts store. It has saved me wasted time and effort ... as two have been bad right out of the box.